Unidirectional battery charge/discharge controller for a regulated electrical bus system with a solar current source

Abstract

In a satellite experiencing alternate periods of light and eclipse, an electrical power control system utilizing direct energy transfer battery charging in a fully regulated electrical bus system to provide and control the system power over both the charging and the discharging cycles of the satellite electrical system.

What is claimed is: 
     
       1. An electrical power subsystem for use with a fully regulated electrical bus system having a voltage bus for providing operating power to a load connected to the bus, comprising: a bus voltage limiter coupled to the regulated bus, the bus voltage limiter operative to maintain bus power at a predetermined level;   an energy storage device;   an at least two section solar array having a first section and a second section, said first section being a current source coupled in parallel with the energy storage device, the current source providing a charging current to the storage device for charging same, said second section coupled through said bus voltage limiter to the regulated electrical bus supplying power to a system load; and   a unidirectional charge/discharge controller having a power stage, said power stage coupled between the first section and energy storage device and said voltage bus, the charge/discharge controller operative to regulate the amount of charging current provided to the energy storage device to provide an optimum current charge in the energy storage device, a power stage responsive to the charge current coupled to the battery and operative to maintain the battery charge at a predetermined level by coupling excess charge current to the regulated voltage bus.   
     
     
       2. The subsystem of claim 1, further including a sensor coupled between the energy storage device and the charge/discharge controller, the sensor operative to determine the amount of charging current required to maintain the optimum charging current in the energy storage device. 
     
     
       3. The subsystem of claim 2 wherein the sensor generated current signal is coupled into the charge/discharge controller, the charge/discharge controller responsive thereto to regulate the amount of charging current coupled into the energy storage device. 
     
     
       4. subsystem of claim 2, wherein the energy storage device is a battery. 
     
     
       5. The subsystem of claim 1, wherein the battery charge/discharge controller is unidirectional and includes: a first error amplifier resistively coupled to the regulated voltage bus, for receiving a signal indicative of the voltage on the regulated bus, and also coupled to a first reference voltage source to develop a first error signal at a first signal output indicative of the regulated voltage;   a second error amplifier coupled to the current sensor, for receiving the generated current signal, and also coupled to a second reference voltage source to develop a second error signal at a first signal output indicative of the charging current; and   the first and second signal outputs resistively coupled into a summing amplifier to combine the signals and provide a control signal output for controlling the charging current to the battery.   
     
     
       6. The subsystem of claim 5, further including: a power stage coupled to receive the battery charge current control signal and operative to couple a part of the charging current to the regulated bus to maintain optimum charge on the battery, the bus voltage limiter operative to compensate for diverting charging current to the regulated bus by reducing the power coupled from the second section of the solar array; and   the power stage further responsive to the control signal to detect reduction of voltage on the regulated bus and to initiate battery discharge to maintain the bus voltage at the predetermined level.   
     
     
       7. The method of controlling an electrical power subsystem for use with a fully regulated electrical bus system, comprising the steps of: providing an electrical storage battery;   charging the battery by directly coupling the output from a first current source into the battery;   monitoring the charge status of the battery and regulating the charging current to maintain the battery charge at optimum by diverting part of the charging current away from the battery.   
     
     
       8. The method of claim 7, wherein the step of monitoring includes: sensing the charge on the battery and developing a signal indicative of the charge status thereof;   coupling the charge status signal into a charge/discharge controller; and   discharging a part of the charging current to reduce the charging of the battery.   
     
     
       9. The method of claim 8, further including the steps of: providing a second current source and coupling the output therefrom to a regulated voltage bus providing load power to the regulated electrical bus system.   
     
     
       10. The method of claim 9, including the step of diverting a portion of the storage device charging current to the regulated voltage bus to maintain the desired charging current on the device. 
     
     
       11. The method of claim 10, further including the steps of: monitoring the charge current on the regulated voltage bus and discharging a portion of the current coupled thereto from the second current source for maintaining optimum current charge on the regulated voltage bus and optimum current charge to charge the storage device.